With this modification, your M52B25 or M52B28 engine will make more power.
The M52B25 and M52B28 engine can be found in the E36, E39, E38, and in some early BMW E46 models. It is not the easiest modification, but if you are at least a little handy, it is not difficult. Some people say that this will gain an additional 20HP, while some say it won’t give you any. I believe that there are power benefits.
In the picture below, you see on the left an M52 intake, and on the right, an M50 intake.